My ford Ranger Is idling To high How do I Fix It

I had the some issue plus mine was running way too rich- black smoke out the exhaust. I did a lot of research and came up with the O2 sensor wasn't reading any more, so I put a new one in and in runs much better. But I advise you to spend the extra $20 and get the better one from Napa or car quest; I put the bosch style in and a few months later it's starting to do it again